Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 2A7, Canada

Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 2A7, Canada

Department of Geography, The Ohio State University, 1036 Derby Hall, 154 N Oval Mall, Columbus, Ohio 43210, USA

Byrd Polar Research Center, the Ohio State University, 108 Scott Hall, 1090 Carmack Road, Ohio 43210, USA

Department of Environmental Studies, University of California, Santa Cruz; 1156 High Street, Santa Cruz, California, 95064, USA

Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 2A7, Canada